Many types of manually operable pumps for dispensing creamy substances are known: some pumps have a very complex structure and are therefore costly, whereas other pumps have a simpler and more economical structure but present the drawback of allowing accidental leakage or emergence of the creamy substance at or about the outer surface of the pump operating and dispensing stem when the pump (mounted on a creamy substance container) is in a downward position relative to the container.